Sealing means for compressor drive shaft



Dec. 18,` 1962 s. G. BEST SEALING MEANS FOR COMPRESSOR DRIVE SHAFT FiledDec. 16, 1959 3,569,173 SEALllNG MEANS FR CMPRESSGR DRVE SHAFT t StanleyG. Best, Manchester, Conn., assignor to United Aircraft Corporation,East Hartford, Conn., a corporation of Delaware Filed Dec. 16, 1959,Ser. No. 859,973 9 Claims. (Cl. 277-3) This invention relates to sealingmeans for preventing fluid leakage along a rotatable shaft and, morespeelfically, to sealing means particularly adapted for preventing gasflow or leakage along the drive shaft of a compressor adapted to handlefluid in a gaseous state.

It is the general object of the invention to provide sealing means ofthe type mentioned which is capable of a more positive sealing actionthan has been obtainable heretofore with sealing means used for asimilar purpose and which is yet free of excessive friction and otherundesirable characteristics in its operation.

The drawing shows two embodiments of the invention and such embodimentswill be described, but it will be understood that various changes may bemade from the construction disclosed, and that the drawing anddescription are not to be construed as defining or limiting the scope ofthe invention, the claims forming a part of this specification beingrelied upon for that purpose.

Of the drawing:

FIG. l is a schematic illustration of a compressor driven by an airturbine and equipped with a preferred form of the sealing means of thepresent invention;

FIG. 2 .is a schematic illustration of an evacuating means and apressure regulating valve means utilized in an alternative form of thesealing means of the invention; and

FIG. 3 is a schematic illustration of a portion of another alternativeform of the invention.

A compressor indicated generally at in FIG. 1 of the drawing is employedin an aircraft air conditioning system and, more particularly, in arefrigeration system forming a part of the aircraft air conditioningsystem. The said compressor handles a refrigerant, such as one of thefreons, in a gaseous state, the refrigerant being introduced to thecompressor through an inlet conduit 12 and discharged therefrom atincreased pressure and temperature through a discharge conduit 14. Thecompressor 10 is driven by an air turbine indicated generally at 16 andconnected with the compressor by a drive shaft 13. The turbine 16 issupplied with propellant air through an inlet conduit 2t) and isprovided with an exhaust or discharge conduit 22 which carries off thespent propellent air.

While the sealing means of the present invention is not limited in itsapplication to refrigerant compressors, its advantages are particularlywell illustrated in a consideration of its use with such a compressor.The freon gas or other refrigerant passing through the refrigerantcompressor in a refrigeration system must not be permitted to escapeoutwardly from the compressor along the compressor drive shaft insignificant quantity. Such refrigeration systems are usually of theclosed cycle type and contain a given quantity of freon gas or otherrefrigerant. Any loss of the refrigerant, as by escape along the driveshaft of the refrigerant compressor, results in a reduction in theefficiency of operation of the refrigeration system. Further, .air orother gas must not be permitted to flow inwardly along the compressordrive shaft so as to become intermixed with the freon or otherrefrigerant handled by the compressor. Pollution of the freon or otherrefrigerant in the refrigeration system by the introduction andintermixing of air or other gas therewlth can be expected to result in areduction in i United States Patent O 3,569,173 Patented Bec. 18, 1962refrigeration system eiiciency and in other undesirable effects.

From the foregoing, it will be apparent that a refrigerant compressor,such as the compressor 10, must be equipped with sealing means capableof positive sealing action in preventing gas ow or leakage bothoutwardly and inwardly along the compressor drive shaft. The sealingmeans of the present invention provides the required positive sealingaction without introducing excessive friction. Generally speaking, thesealing means of the invention comprises a sealing device adapted torestrict the ow of gas along the compressor drive shaft and meansdefining iirst and second annular chambers disposed respectively onopposite or inboard and outboard sides or" said sealing device. Theinboard chamber receives the fluid to be sealed (Le. compressordischarge gas) and the outboard chamber is connected by a suitable fluidpassageway with a source of fluid and preferably a gas under pressure. Apressure regulating valve means included in the sealing means isoperable to maintain substantially a zero pressure difference betweenthe first and second or inboard and outboard chambers and across thesealing device therebetween. With substantially a zero pressuredifference thereacross, the sealing device is able to provide positivesealing action with substantially no gas flow or leakage either inwardlyor outwardly along the drive shaft. Moreover, the sealing device doesnot have to be of an extremely tight fitting type with high frictioncharacteristics in order to provide the necessary positive sealingaction.

ln FiG. 1 of the drawing it will 'oe observed that the compressor l@ isprovided with a housing or casing 24 which is connected with the inletand discharge conduits i2 and 14 and which has a fluid tight connectionwith an inner end portion 26 of a drive shaft housing or sleeve 28. Theouter end portion 3i) of the shaft housing or sleeve 28 has fluid tightconnection with a turbine housing or casing 32. As shown, the housing orsleeve 28 is generally cylindrical and its inner end portion 26 is ofsubstantially larger diameter than the remaining portion thereof. Anannular chamber 34 defined within the inner end portion 26 of the sleeveconstitutes the aforementioned first or inboard annular chamber and saidchamber is adapted to receive compressor discharge gas as will beexplained hereinbelow.

The rst or inboard chamber 34 may receive a flow of compressor dischargegas in a comparatively unrestricted manner or, the flow of compressordischarge to the said chamber may be restricted. In accordance with thepresently preferred practice, the flow of compressor discharge gas orrefrigerant to the chamber 34 is restricted by a first continuouslyoperable sealing device indicated generally at 36 and comprising anannular sealing element 38. The annular sealing element 33 may takevarious forms within the scope of the invention, but is preferably ofthe labyrinth type and is shown supported by a radially inwardlyextending annular flange 40 formed integrally at the inner end of theend portion 26 of the sleeve 28. The element 38 continuously engages theouter periphery of an axially extending annular flange 42 formedintegrally on the rear face of a rotor 4.4 of the compressor 10.

It will be apparent that gaseous refrigerant discharged from thecompressor 1t) will flow radially inwardly along the rear face of therotor 44 to the area adjacent the inner side of the labyrinth seal 38.The flow of gaseous refrigerant into the chamber 34 or outwardly alongthe shaft 18 is restricted bythe seal 38, but there is a signicant flowor leakage past the said seal and into said chamber. Obviously,refrigerant pressure in the chamber 34 will increase substantially tothe compressor discharge level with the passage of time if there is noavenue of escape in the chamber for the gaseous refrigerant. While theinvention is not so limited, such pressure build up of gaseousrefrigerant in the chamber 34 is not permitted in the preferred form ofsealing means shown in FIG. 1. Means defining a fiuid passagewayconnecting the chamber 34 with the inlet side of the compressor Si@ isprovided and, as shown, said means comprises a conduit 46 which extendsbetween said chamber and the compressor inlet conduit 12. The capacityof the conduit 46 is sufiicient to provide for a refrigerant pressure inthe chamber 34 substantially equal to compressor inlet pressure. Thatis, the said conduit can accommodate sufficient flow of gaseousrefrigerant from the chamber 34 to the inlet side of the compressor toprevent pressure build up in said chamber as a result of the continuingintroduction of compressor discharge refrigerant to the chamber past thelabyrinth seal 38.

Preferably but not necessarily, a static sealing device is provided toprevent the flow of gas along the drive shaft 18 when the said shaft isat rest. is indicated generally at 48 and is shown located within theinboard chamber 34. The construction and operation of said device willbe explained fully hereinafter and for the present, it is only necessaryto observe that the said device is inoperative during rotation of thedrive shaft 18 and that gaseous refrigerant in the chamber 34 ispermitted to flow outwardly along the drive shaft 18 past the deviceduring such periods of shaft rotation.

Disposed outwardly of the static sealing device 48 along the shaft 18 isa second continuously operable sealing device indicated generally at 50.The said continuously operable sealing device constitutes theaforementioned sealing device across which a substantially zero pressuredifference is maintained. Preferably and as shown, the sealing device f!comprises an annular sealing element 52 which may be a carbon orgraphite ring seal of the well known type. The sealing device alsocomprises a seal support ring 54 which is secured to the sleeve 28 andwhich supports the sealing element 52 in engagement with the outerradial face of an annular flange 56 formed on the compressor drive shaft18. Spring means (not shown) may be incorporated to bias the element 52into engagement with the face of the flange 56 in accordance withconventional practice. With substantially a zero pressure differenceprovided across the sealing element 52 in a manner to be described, itwill ybe seen that a positive sealing action with substantially no gasfiow along the shaft in either direction past said element can beeffected without an excessively tight and high friction fit between theelement and the iiange 56.

An annular chamber 58 is defined within the sleeve 28 outwardly of thecontinuously operable sealing device 5f) and constitutes theaforementioned outboard chamber in which a gas pressure is regulated inorder to maintain substantially a zero pressure difference across saidsealing device. The chamber 58 extends outwardly from the sealing device50 about the shaft 18 and within the sleeve 28 and is further defined bya central portion of a rotor 60 of the turbine 16. Disposed within thechamber 58 and supported by the sleeve 28 are axially spaced inner andouter bearing units 62, 62 which rotatably support the compressor driveshaft 18. Outwardly of the outer bearing unit 62, the shaft 18 isprovided with an integrally formed annular flange 64 and associated withsaid fiange is a third continuously operable sealing device 66. Thesealing device 66 is shown as comprising a support ring 68 which issecured to the sleeve 18 and which carries an annular sealing element 7t) which may be a spring loaded carbon or graphite ring seal. Thesealing element 70 engages the outer radial face of the annular flange64 and restricts gas flow along the shaft 18 for a purpose to be setforth more fully hereinbelow. Outwardly of the sealing device 68, thesleeve 18 supports an annular sealing element 72 which may be of thelabyrinth type as shown and which engages the outer periphery of anaxially extending annular ange Y74 formed on the turbine rotor 60.

Such a sealing device It will be apparent that a gas under pressure maybe introduced to the outboard chamber 58 and it will be further apparentthat the pressure of the gas may be regulated to substantially equal thepressure of the gaseous refrigerant in the inboard chamber 34 whereby toprovide substantially a zero pressure difference across the continuouslyoperable sealing device Sti. As mentioned, a regulating valve means forcontrolling pressure in the outboard chamber 58 is provided and saidchamber is connected with a source of gas under pressure by suitablefluid passageway means. In the preferred form of sealing means shown inFIG. l, a conduit 76 communicates with the outboard chamber 58 andextends therefrom to a pressure regulating valve indicated generally at78. The pressure regulating valve 78 is connected with a supply conduit8f) which communicates with a source of air or other gas under pressure(not shown). Also connected with the pressure regulating valve 7 S is aconduit 82 which extends therefrom to the aforementioned conduit 46 andwhich is thus indirectly connected with the inboard chamber 34?.

As shown, the pressure regulating valve 78 comprises a valve member 84of the poppet type which is movable in one and an opposite direction(rightwardly and leftwardly as shown) to vary the effective area oropening of an orifice 86. The orice 86 is defined at the free end of thesupply conduit and within a valve chamber 88 which communicates with theconduit 76. Thus, movement of the poppet valve 84 in said one andopposite directions is effective to vary the fiow of air from theconduit 88 to the valve chamber 88, the conduit 76, and the outboardchamber 58. A valve stem 90 connected at one end to the poppet valve 8dhas its opposite end connected to a valve control means comprising abellows 92 disposed within the valve chamber S8. The bellows 92 receivesgaseous refrigerant from the inboard chamber 34 through the conduits 46and 82 for action on its inner surfaces, the outer surfaces of saidbellows being acted on by air in the valve chamber 88 at a pressuresubstantially equal to the pressure of the air in the outboard chamber58.

From the foregoing, it will be apparent that the poppet valve 84 will bemoved relative to the orifice 86 as ren quired to provide forsubstantially zero pressure difference between the outboard chamber 58and the inboard chamber 34 and across the continuously operable sealingdevice 5t). If the pressure of the gaseous refrigerant in the inboardchamber 34 exceeds the air pressure in the outboard chamber 58, theresultant pressure forces on the regulating valve bellows 92 will causethe said bellows to expand. Expansion of the bellows 92 will result inrightward movement of the poppet valve 84 and an increased effectiveopening of the orifice 86. An increase in the flow of pressurized airthrough the valve chamber 88 and the conduit 76 to the outboard chamber58 will result and the air pressure in said chamber will be increased toequal the pressure of the gaseous refrigerant in the chamber 34.Conversely, if the air pressure in the outboard chamber 58 exceeds thepressure of the gaseous refrigerant in the inboard chamber 34, the valvebellows 92 will collapse moving the poppet valve 84 leftwardly andreducing the effective opening of the orifice 86. This will result in adecreased ow of pressurized air to the outboard chamber 58 and thepressure in said chamber will be reduced to equal the pressure of thegaseous refrigerant in the inboard chamber 34.

It will be observed that the pressurized air within the outboard chamber58 can only escape from the said chamber past the labyrinth seal 72 4atthe outer end of the sleeve 28. It can be expected that only arelatively small flow of air past the seal 72 will occur. Thus, the flowof pressurized air through the regulator valve 78 to the outboardchamber 58 will be slight and the said poppet valve, for yall practicalpurposes, will completely close the orifice 86 and terminate air owtherethrough when the regulator valve is operating Ito reduce airpressure within the outboard chamber 58. With the poppet valve 84closing the orifice 86, the leakage flow outwardly past the labyrinthseal 72 results in the necessary reduction in the air pressure in theoutboard chamber 58 and it is to be noted that air can be expected toflow from the inner to the outer end portion of the said chamber towardsaid labyrinth seal. That is, pressurized air in the inner end portionof the chamber S8 can be expected to flow past the outer bearing unit 62and the sealing device 66 toward the labyrinth seal 72. Such air flowpast the outer bearing unit 62 may have detrimental effects on saidbearing unit particularly with respect to its lubrication and it istherefore the presently preferred practice to prevent the flow of airover the outer bearing unit in the manner described hereinbelow.

A bypass conduit 94 is provided `and extends between the conduit 76 andthe outer end portion of the chamber 58. Said bypass conduitcommunicates with the chamber 58 outwardly `of the aforementionedsealing device 66 and the outer bearing unit 62 and provides analternative path for pressurized air flowing from the inner to the outerend portion of the chamber 58 whereby the air is not required to flo-wpast the said outer bearing unit and sealing device. The resistance toair flow provided by the sealing device 66 is substantially greater thanthe resistance encountered by the pressurized air in the alternativepath through the conduit 76 and the bypass conduit 94. Thus, it can beexpected that there will be substantially no air flow past the outerbearing unit 62 and the sealing device 66 and the detrimental effects ofair flow past the said bearing unit will be avoided.

The provision of the previously mentioned static sealing device isoptional as indicated and, when provided, the said device may take avariety of forms. Obviously, the continuously operable sealing device 50is relieved of the task o-f static sealing when the sealing device 48 isprovided. As a result, said continuously operable sealing device may bespecifically designed to provide positive sealing action only duringperiods of shaft rotation and with substantially a zero pressuredifference thereacross. This permits a sealing device design whereinminimum friction is encountered with the desired positive sealing actionduring drive shaft rotation.

As shown, the static sealing device 48 comprises an annular sealingelement 96 which may be a carbon or graphite ring seal. The said sealingelement engages the inner radial face of the annular flange 56 on thedrive shaft 18 and is carried by a support ring 98 which has one endportion of a bellows 100 secured to its peripheral portion. The otherend portion of the bellows 100 is secured to a radial wall 102 of thesleeve 28 yand said bellows cooperates with the support ring 98, saidradial wall of the sleeve 28, the support ring 54 of the sealing device50, and the annular flange 56 on the shaft 18 to define a gas tightpassageway 104 which extends between the sealing element 96 and thesealing element 52 of the sealing device 50. It will be observed thatgas flow or leakage either inwardly or outwardly along the shaft 18 pastits flange S6 can only occur through the passageway 104. The saidpassageway is closed to gas flow or leakage at its outer end by theannular sealing element 52 during rotation of the shaft 18 in the mannerdescribed above. The annular sealing element 96 is adapted to close saidpassageway to gas flow or leakage at its inner end when the shaft 18 andthe compressor 10 are at rest but when said shaft and compressor arerotating, the element 96 is moved out of engagement with the flange 56and opens the inner end of the passageway 104 to the flow of gas.

A first or outer sleeve 106 of the sealing device 48 is secured to theshaft 1S by means of a key 108 and is adapted to be rotated with saidshaft but is movable axially along the shaft, a keyway 110 whichreceives the keg/,108 being of sufficient length to permit such axialmovement. Provided in the sleeve 106 is an annular recess 112 whichreceives the inner portion of the aforesaid support ring 98. The radialwalls of the recess 112 engage the adjacent radial faces of the supportring 98 on axial movement of the sleeve 106 so as to move the saidsupport ring axially with said sleeve. The sleeve 106 is freelyrotatable relative to the said support ring, the bellows 100 orpreferably other means not shown serving to secure the said ring againstrotation.

Spaced axially inwardly along the shaft 18 from the first or outersleeve 106 is a second or inner sleeve 114 which is connected to thesaid shaft by a key 116. The inner sleeve 114 is rotatable with theshaft 18 and is fixedly secured against axial movement relative to saidshaft by the key 116 and a cooperating keyway 117. A spring 118 disposedabout the shaft 18 between the inner and outer sleeves 114 and 106biases the sleeve 106 outwardly along said shaft whereby to bias thesupport ring 98 outwardly and urge the annular sea'ing element 96 intoengagement with the inner face of the annular flange 56 to close theinner end of the passageway 104.

A centrifugally operable means comprising a flyweight 120 and connectedlinks 122 and 124- urges the sleeve 106 inwardly along the drive shaft18 whereby to cause the annular sealing element 96 to open the inner endof the passageway 184. The link 122 is pivotally connected to the innersleeve 114;- at one end and pivotally connected at its opposite end toone end of the l'nk 124, the opposite end of the link 124 beingpivotally connected to the outer and axially movable sleeve 106. Theflyweight 120 is connected Vto the links 122 and 124 at their pivotalconnection with each other and serves to urge their interconnected endsradially outwardly as the shaft 18 is rotated. Thus, the inner end ofthe link 124 is drawn axially inwardly along the shaft 18 duringrotation of said shaft to move the sleeve 106 and Vthe elementssupported thereby axially inwardly as described and open the inner endof the passageway 104. Axial flow of gas past the sleeve 106 to saidpassage- Way inner end may obviously take place either between saidsleeve and the shaft 18 or between the sleeve and the aforementionedsupport ring 98.

From the foregoing, it will be apparent that the annular sealing element96 is biased into sealing engagement with the annular flange S6 when theshaft 18 is at rest and closes the inner end of the passageway 104. Whenthe shaft 18 is rotated, the sealing element 96 is moved axiallyinwardly out of engagement with the inner face of the flange 56 to openthe passageway 104 by action of the centrifugally operable meanscomprising the flyweight 120 and the links 122 and 124. Thus, the staticsealing device 48 is operable to prevent gas flow or leakage inwardlyand outwardly along the shaft 18 when the shaft is at rest, but the saiddevice is inorerative for such purpose when the shaft is rotated. Sincethe sealing element 96 of said device is disengaged from the flange 56during rotation of the shaft, frictional Wear of said sealing element isinsignificant. Positive sealing action of the element 96 with the flange56 with substantially no gas leakage or flow along the shaft past saidelement and flange can be readily provided for by utilizing a biasingspring 118 of substantial strength.

The preferred form of seaing means described above provides positivesealing action with substantially no gas flow or leakage either inwardlyor outwardly along a compressor drive shaft during operation of thecompressor and also during periods when the compressor is at rest.Moreover, the positive sealing action is obtained without an excessivelytight and high friction fit between the sealing element 52 and the driveshaft flange 56 which is continuously engaged by said element. As aresult, friction induced wear of the element is reduced and itseffective life is substantially increased. The sealing element 96 in thestatic sealing device 48 can be expected to exhibit excellent wearcharacteristics in view of the absence of any signiticant rubbingengagement of said element with the shaft ange 56. The remaining sealingelements included in the sealing means are not required to providepositive sealing action and may there fore be designed for low frictioncharacteristics and long life.

The above-mentioned features and advantages of the preferred form ofsealing means are particularly desirable in a refrigerant compressor ofthe type shown. However, the said sealing means has one limitation whichmay be unacceptable in certain refrigerant compressor installations andin some other installations of the sealing means as well. The regulatingvalve 78 is incapable of providing air pressure in the outboard chamber58 which is lower than atmospheric pressure. In certain refrigerationsystems, compressor inlet pressure may be reduced to a subatmospherielevel and it will be obvious that the pressure in the inboard chamber 34will be correspondingly reduced. In such event, the air in the outboardchamber 58, at atmospheric pressure or above, might conceivably leakinwardly along the shaft 18 past the sealing device t) due to thepressure difference occurring across said device. As mentioned above,the introduction of air to the freon gas or other refrigerant results inpollution of such gas or refrigerant which may cause an unacceptablereduction in the efiiciency of operation of the refrigeration system.

In FIG. 2 there is shown a pressure regulating valve indicated generallyat 126 and an evacuating means indicated generally at 12S. The saidpressure regulating valve and evacuating means are adapted for use in analternative form of the sealing means of the present invention, the saidalternative form of the sealing means being particularly adapted toavoid the above-mentioned' limitation of the preferred form of thesealing means. All elements of the alternative form of the sealing meansmay be identical with those described above in the preferred form ofsealing means with the exception of the regulating valve 78. The saidregulating valve is replaced in the alternative form of the sealingmeans by the regulating valve 126 and the evacuating means 128 is addedthereto. Accordingly, only the regulating valve 126 and the evacuatingmeans 128 are shown in FIG. 2, a repetitive illustration of theremaining elements of the sealing means being deemed unnecessary.

The regulating valve 126 has an air chamber 13G defined therewithin anda bellows 132 is disposed within said chamber. A conduit 76acommunicating with the air chamber 130 of the regulating valve 126correspo-nds to the conduit 76 of FIG. l and may be similarly connectedwith the outboard chamber 53 in FIG. l. A conduit 82a communicating withthe interior of the bellows 132 corresponds to the conduit 82 in FIG. land may be similarly connected to the inboard chamber 34. The bellows132 is operatively connected with a pivotally supported elongated valvemember or lever 134 by means of a link 136. Expansion of the bellows 132pivots the valve member or lever 134 about a pivot or fulcrum 138 in aclockwise direction as shown and results in a decreased effectiveopening of an associated orifice 149 and an increased effective openingof an associated orifice 142. The orifice 146 is defined at the free endof a conduit 144 which is connected with the evacuating means 128 andthe orifice 142 is defined at the free end of a branch conduit 146. Thebranch conduit 146 extends from a supply conduit 80a which correspondsto the supply conduit 80 in FIG. l and which is similarly connected witha source of air or other gas under pressure.

It will be apparent that the regulating Valve 126 will operate tobalance refrigerant gas pressure in the inboard chamber 34 over a rangeof pressures including subatmospheric pressures. That is, the regulatingvalve 126 will provide subatmospheric air pressures in the outboardchamber 58 as required to balance and equal subatmospheric refrigerantpressures in the inboard chamber 34 and provide substantially a zeropressure difference across the continuously operable sealing device Silbetween said chambers. When the refrigerant pressure in the inboardchamber 34 is above atmospheric pressure, the bellows 132 will expand asshown in FIG. 2 to adjust the position of the valve member or level 134to reduce the effective opening of the orifice 141i and increase theeffective opening of the orifice 142. Pressurized air will be suppliedfrom the conduit a and the branch conduit 146 through the orifice 142 tothe conduit 76a and to the outboard chamber 58 as required to providefor substantially a zero pressure difference between the inboard andoutboard chambers and across the sealing device 5t). When therefrigerant pressure in the inboard chamber is subatmospheric, thebellows 132 will be collapsed from the position shown and the orice 142will be closed by the valve lever 134 while the orifice 140 is openedthereby. Pressurized air will fiow from the outboard chamber S8 throughthe conduit 76, the valve chamber 13), the orifice 143 and to theevacuating means 128 and the pressure in said outboard chamber will bereduced to provide substantially a zero pressure difference between theinboard and outboard chambers and across the sealing device SQ.

The evacuating means 128 included in the alternative sealing means ofthe invention may take various forms. Preferably the said meanscomprises a jet pump device as shown, the conduit 30a being formed witha suitable orifice 148 which is disposed within the conduit 144 andadapted to induce air flow in said conduit away from the orifice 146.The conduit 144 may be provided with a venturi section 150 as shown toenhance the efiiciency of the orifice or nozzle 148.

In FIG. 3 a portion of a second alternative form of the sealing means ofthe present invention is illustrated. In this form of the sealing meansthe conduit 46 extending between the inboard chamber 34 and the inletside of the compressor 10 is provided with a branch conduit 152 whichcommunicates with the discharge side of the compressor. A restriction154 is provided in the conduit 46 between the inlet side of thecompressor and the branch conduit 152 and a restriction 156 is providedin said branch conduit. The relative sizes of the restrictions 154 and156 or the relative areas of associated orifices 158 and 166 are suchthat the gaseous pressure therebetween and in the inboard chamber 34 ismaintained between the compressor inlet and discharge pressure and abovea predetermined level. Obviously, said predetermined pressure level maybe selected at a value above atmospheric and so that the inboard chamberpressure will not drop below the lowest pressure obtainable in theoutboard chamber 53 with the use of the regulating valve 78 of FIG. l.The aforementioned harmful inward leakage of air along the shaft 18 willthus be positively prevented and contamination of refrigerant will beavoided.

From the foregoing, it will be apparent that each of the alternativeforms of sealing means of the present invention provides all of thefeatures and advantages of the aforedescribed preferred form of sealingmeans of FIG. l. In addition, the said alternative forms of sealingmeans include provisions whereby substantially a zero pressuredifference can be maintained across a continuously operable sealingdevice over a wide range of pressures extending to subatmosphericlevels. In consequence, positive sealing action with desirably lowfrictional characteristics can be obtained for all conditions ofoperation ordinarily encountered in the sealing of a refrigerantcompressor drive shaft or the like.

The invention claimed is:

1. In a gaseous fiuid compressor which may receive gaseous fluid atsubatmospheric pressures and which includes a rotatable drive shaft, thecombination of a first sealing device adapted to restrict the flow ofgas along the shaft, a second sealing device spaced outwardly along theshaft from said first sealing device and also adapted Chi to restrictthe fiow `of' gas therealong, means defining first and second annularchambers disposed about the drive shaft respectively on inboard andoutboard sides of said second sealing device, said inboard chamber beingadapted to receive compressor discharge gas fiowing outwardly past saidfirst sealing device, means defining a first fluid passageway connectingsaid inboard chamber with the inlet side of the compressor whereby toprovide for gas pressure in said chamber substantially equal tocompressor inlet pressure, means defining a second fluid passagewayconnected with said outboard chamber, a source of air under pressure,evacuating means, and pressure regulating valve means connected withsaid first and second fluid passageways, and connectible with saidsource of air under pressure and said evacuating means, said valve meansbeing operable responsive to pressure difference between said first andsecond passageways and said inboard and outboard chambers to selectivelyconnect said second passageway with said source of air under pressureand said evacuating means whereby to regulate pressure in said outboardchamber so as to maintain substantially zero pressure difference betweensaid chambers and across said second sealing device.

2. In a gaseous iiuid compressor which may receive gaseous iiuid atsubatmospheric pressures and which includes a rotatable drive shaft, thecombination of a first sealing device adapted to restrict the flow ofgas along the shaft, a second sealing device spaced outwardly along theshaft from said first sealing device and also adapted to restrict thefiow of gas therealong, means defining first and second annular chambersdisposed about the drive shaft respectively on inboard and outboardsides of said second sealing device, said inboard chamber being adaptedto receive compressor discharge gas flowing outwardly past said firstsealing device, means defining a first iiuid passageway connecting saidinboard chamber with the inlet side of the compressor whereby to providefor gas pressure in said chamber substantially equal to compressor inletpressure, means defining a second iiuid passageway connected with saidoutboard chamber, pressure regulating valve means connected with saidfirst and second iiuid passageways, means defining a third fluidpassageway connected with a source of air under pressure and with saidvalve means, means defining a fourth fluid passageway connected withsaid valve means, and a jet pump in said fourth fluid passagewayconnectible with a source of air under pressure and adapted to provide asubatmospheric pressure in said fourth fluid passageway, said pressureregulating valve means being operable responsive to pressure differencebetween said first and second passageways and inboard and outboardchambers to selectively connect said second fluid passageway with saidthird and fourth fluid passageways whereby to regulate pressure in saidoutboard chamber so as to maintain substantially Zero pressuredifference between said chambers and across said second sealing device.

3. In a gaseous iiuid compressor which includes a rotatable drive shaft,the combination of a first sealing device adapted to restrict the flowof gas along the shaft, a second sealing device spaced outwardly alongthe shaft from said first sealing device and also adapted to restrictthe flow of gas therealong, means for defining first and second annularchambers disposed about the drive shaft respectively on inboard andoutboard sides of said second sealing device, said inboard chamber beingadapted to receive compressor gas fiowing outwardly past said firstsealing device, means defining a fluid passageway connected with saidoutboard chamber and connectible with a source of gas under pressure, avalve in said passageway adjustable between open and closed positionsfor controlling the fiow of gas to said outboard chamber, valve controlmeans connected by iiuid passageway means with said inboard and outboardchambers and operable responsive to pressure difference between saidchambers to adjust the position of said valve whereby to control fiow 10to the outboard chamber and to maintain substantially a zero pressuredifference between said chambers for inboard chamber pressures aboveatmospheric pressure, and means for maintaining the pressure of gas insaid inboard chamber above atmospheric pressure.

4. In a gaseous fluid compressor which includes a rotatable drive shaft,the combination of a first sealing device adapted to restrict the fiowof gas along the shaft, a seco-nd sealing device spaced outwardly alongthe shaft from said first sealing device and also adapted to restrictthe fiow of gas therealong, means for defining first and second annularchambers disposed about the drive shaft respectively on inboard andoutboard sides of said second sealing device, said inboard chamber beingadapted to receive compressor gas flowing outwardly past said fisrtsealing device, means defining a rst fluid passageway connesting saidinboard chamber with the inlet side of the compressor, means defining abranch passageway connecting said first fluid passageway with thedischarge side of said compressor, passageway restricting means disposedin said first and branch passageways so as to provide for 1an inbo-ardchamber pressure which ranges between compresser inlet and dischargepressure but which always excee-ds atmospheric pressure, means, defininga second fluid passageway connected with said outboard chamber andconnectible with a source of gas under pressure, a valve in said secondpassageway adjustable between open and closed positions for controllingthe flow of gas to said outboard chamber, and valve control meansconnected with said first and second passageways and operable responsiveto pressure difference between said inboard and outboard chambers toadjust the position of said valve whereby to control fiow to theoutboard chamber as required to maintain substantially a zero pressuredifference between said chambers and across said second sealing device.

5. In a gaseous iiuid compressor which includes a rotatable drive shaft,the combination of a continuously operable sealing device whichrestricts the flow of gas along the drive shaft, means defining firstand second annular chambers disposed about the drive shaft respectivelyon inboard and outboard sides of said sealing device, said inboardchamber receiving gas from the discharge side of the compressor, meansdefining a iiuid passageway for connection of said outboard chamber witha source of gas under pressure, pressure regulating valve meansconnected by fluid passageway means with said inboard and outboardchambers and operable responsive to pressure difference therebetween toregulate pressure in said outboard chamber whereby to maintainsubstantially a zero pressure difference between said chambers andacross said sealing device, and a static sealing device operativelyassociated with said drive shaft and adapted to restrict the fiow of gasthereaiong when the shaft is at rest, said sealing device beinginoperative when said shaft is rotating.

6. In a gaseous iiuid compressor which includes a rotatable drive shaft,the combination of a continuously oper- -able sealing device whichrestricts the fiow or gas along the drive shaft, means defining firstand second annular chambers disposed about the drive shaft respectivelyon inboard and outboard sides of said sealing device, said inboardchamber receiving gas from the discharge side of the compressor, meansdefining a iiuid passageway for connection of said outb-oard chamberwith a source of gas under pressure, pressure regulating valve meansconnected by iiuid passageway means with said inboard and outboardchambers and operable responsive to pressure difference therebetween toregulate pressure in said outboard chamber whereby to maintainsubstantially a zero pressure difference between said chambers andacross said sealing device, and a centrifugally operable sealing deviceassociated with said drive shaft on the inboard side of saidcontinuously operable sealing device and adapted to restrict the tiow ofgas therealong when the shaft is at rest and to permit the free flow ofgas along said shaft during rotation thereof.

7. in a gaseous fluid compressor which includes a rotatable drive shaft,the combination of a continuously operable sealing device whichrestricts the flow of gas along the drive shaft, means defining firstand second annular chambers disposed about the drive shaft respectivelyon inboard and outboard sides of said sealing device, said inboardchamber receiving gas from the discharge side of the compressor, meansdefining a iuid passageway for connection of said outboard chamber witha source of gas under pressure, pressure regulating valve meansconnected by iiuid passageway means with said inboard and outboardchambers and operable responsive to pressure difference therebetweentoregulate pressure in said outboard chamber whereby to maintainsubstantially a zero pressure difference between said chambers andacross said sealing device, and a static sealing device in said inboardchamber comprising a sealing element spring biased in sealing engagementwith said drive shaft but movable out of sealing engagement by action ofa connected centrifugally operable means and a iiexible closure meansdefining a gas tight fluid passageway about said shaft between saidsealing element and said continuously operable sealing device.

8. In a gaseous iiuid compressor which includes a rotatable drive shaft,the combination of a first continuously operable sealing device adaptedto restrict the flow of gas along the drive shaft, a second continuouslyoperable sealing device spaced outwardly along said shaft from saidfirst sealing device and also adapted to restrict the flow of gastherealong, means defining first and second annular chambers disposedabout the drive shaft respectively on inboard and outboard sides of saidsecond sealing device, said inboard chamber being adapted to receivecompressor discharge gas flowing outwardly past said first sealingdevice, means defining a first iiuid passageway connecting said inboardchamber with the inlet side of the compressor whereby to provide for gaspressure in said chamber substantially equal to compressor inletpressure, means defining a second fluid passageway connected with saidoutboard chamber, a source of air under pressure, evacuating means,pressure regulating valve means connected with said first and secondfiuid passageways and connectible with said source of air under pressureand said evacuating means and operable responsive to pressure differencebetween said inboard and outboard chambers to selectively connect saidsecond passageway with said source of air under pressure and saidevacuating means whereby to regulate pressure in said outboard chamberso as to maintain substantially zero pressure difference between saidchambers and across said second sealing device, and a static sealingdevice opera- 12 tively associated with said drive shaft `and adapted torestrict the iiow of gas therealong when the shaft is at rest, saidsealing device being inoperative when said shaft is rotating.

9. In a gaseous iiuid compressor which includes a rotatable drive shaft,the combination of a first continuously operable sealing device adaptedto restrict the fiow of gas along the drive shaft, a second continuouslyoperable sealing device spaced outwardly along the shaft from said firstsealing device and also adapted to restrict the of tiierealong, meansdefining first and second annular chambers disposed about the driveshaft respectively on inboard and outboard sides of said second sealingdevice, said inboard chamber being adapted to receive compressordischarge gas flowing outwardly past said first scaling device, meansdefining a first fiuid passageway connecting said inboard chamber withthe inlet side of the compressor whereby to provide for gas pressure insaid chamber substantially equal to compressor inlet pressure, meansdefining a second fluid passageway connected with said outboard chamber,pressure regulating valve means in said second fluid passageway andconnected with said first passageway, means defining a third fiuidpassageway connectible with a source of air under pressure and with saidvalve means, means defining a fourth liuid passageway connected withsaid valve means, a jet pump in said fourth iuid passageway connectedwith a source of air under pressure and adapted to provide asubatrnospheric pressure in said passageway, said pressure regulatingvalve means being operable responsive to pressure difference betweensaid inboard and outboard chambers toselectively connect said secondiiuid passageway with said third and fourth uid passageways whereby toregulate pressure in said outboard chamber so as to maintainsubstantially zero pressure difference between said chambers and acrosssaid second sealing device, and a static sealing device in said inboardchamber comprising a sealing element spring biased in sealing engagementwith said drive shaft but movable out of sealing engagement by action ofa connected centrifugally operable means and a flexible closure meansdefining a gas tight fluid passageway about said shaft between saidsealing element and said second continuously operable sealing device.

References Cited in'the file of this patent UNITED STATES PATENTS1,353,095 Uttech et al. Sept. 14, 1920 2,895,750 Gardner et al. July 2l,1959 2,911,919 Tucker Nov. 10, 1959 2,913,989 Boardman et al Nov. 24,1959

